How to build a pulse truncator?

Sorry. Your 0.2% is the worst case for the military part. the obtainalbe parts offered a worst case of 0.5% per volt.

Colin explained the application to me at the time, but it didn't make much sense to me then, and I've completely forgotten the explanation in the meantime. He was fond of pulse width modulation and had worked out some really strange ways of producing stable and adjustable mark-to-space ratios, and I thnk the stable astable was involved.

This was shortly before CMOS logic suddenly became affordable - the following year I built a 10-bit PWM D/A converter around a pair of CD4040 counters, which ended up in a couple of U.K. power stations.

IIRR the desired accuracy would have been around +/-0.1% over a 0C to

In a NEW design ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

With all due respect, I was still talking about hobby projects. The stuff you cobble together with parts out of the junk box on a rainy sunday afternoon.

If the 40106 breaks (theoretically possible, but usually they far outlast the RC application they are used in) - I stuff a new one in, and if luck is against me - I might even change a resistor value too.

We are talking 555 alternatieves here! Not life support systems.

If timing is more critical, I get a 4060. If it is truly serious, I might get out a Tiny15 or such, mostly overkill. I guess I have been very lucky for a very long time. It works very well for me, but YMMV a lot.

Don't tick me off, or I'll clean your clock.

John

(It's high time we had a pun thread!)

Wouldn't surprise me.

I recently got a call from Raytheon (the old Hughes Tucson) asking where to obtain a quantity of chips I designed in the mid-60's ;-)

...Jim Thompson

Yes, and small quantity production of OLD existing designs. The quantity-in-stock of TTL tells a story. A lot of zeros there..

Best regards, Spehro Pefhany

Of course, this does introduce a possible source of variation if the output loading could change. With the original bipolar device, the output-high voltage was fairly sensitive to temperature, too (darlington emitter follower).

-f

--- Well, I just checked Digi-key for 74HC00 and found 112743 pieces there, so _something's_ wrong...

Maybe you guys are talking bipolar TTL?

-- John Fields Professional Circuit Designer

Hmmmm? There's CMOS TTL??? I don't think so ;-)

There's TTL-threshold-compatible CMOS, as in 74HCT00, but the output swing is still rail-to-rail.

...Jim Thompson

Well, if ya' wanna get really picky very little of the "TTL" line is really TTL. Most are SDTL.

Yes, and the don't have to be run at 5V either.

Certainly. But the physical architecture of CMOS logic is nothing like bipolar transistor-transistor.

...Jim Thompson

And he'll need one for each of Q and ~Q, maybe diode-or'd together.

Cheers! Rich

He _did_ say it's a one-off hobby project. They're jim-dandy for that; I'm not ready to try to plug a TSOP chip (or whatever those little thingies are called) into my proto-board! ;-)

Cheers! Rich

Have a good one John !!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |